The present invention relates to a method of overwrapping packets.
The present invention may be used to advantage in the tobacco industry for overwrapping packets of tobacco products, in particular packets of cigarettes, to which the following description refers purely by way of example.
More specifically, the present invention relates to a method (for example as disclosed in EP 0135818) of overwrapping packets substantially in the form of a rectangular prism defined axially by two opposite end surfaces, and laterally by two major lateral surfaces and two minor lateral surfaces parallel to a longitudinal axis of the rectangular prism; the packets being overwrapped as they are fed, in a given feed direction, along a given wrapping path; and the method comprising, for each packet, a pairing step to pair the packet with a relative sheet of wrapping material; a first folding step to fold the sheet of wrapping material into a U about the packet so that the sheet has two projecting lateral portions, each projecting from a respective said end surface; a second folding step to further fold the sheet of wrapping material about the packet and form, about the packet, a tubular wrapping comprising two tubular appendixes projecting from respective said end surfaces of the packet and defined by said two projecting portions of the sheet; a sealing step to stabilize said tubular wrapping; and a third folding step to fold each said tubular appendix onto the respective end surface of the packet to obtain a closed overwrapping; said packet being fed continuously along said wrapping path; and each said projecting lateral portion of the sheet of wrapping material being folded at least partly onto the relative said end surface prior to said second folding step.
It is an object of the present invention to perfect the above known method to speed up the wrapping procedure, and to minimize and at the same time simplify the devices required to perform the wrapping procedure.
According to the present invention, there is provided a method of overwrapping packets substantially in the form of a rectangular prism defined axially by two opposite end surfaces, and laterally by two major lateral surfaces and two minor lateral surfaces parallel to a longitudinal axis of the rectangular prism; the packets being overwrapped as they are fed, in a given feed direction, along a given wrapping path; the method comprising, for each packet,
a pairing step to pair the packet with a relative sheet of wrapping material;
a first folding step to fold the sheet of wrapping material into a U about the packet so that the sheet of wrapping material has two projecting lateral portions, each projecting from a respective said end surface;
a second folding step to further fold the sheet of wrapping material about the packet and form, about the packet, a tubular wrapping comprising two tubular appendixes projecting from respecttive said end surfaces of the packet and defined by said two projecting lateral portions; a sealing step to stabilize said tubular wrapping;
and a third folding step to fold each said tubular appendix onto the respective end surface of the packet to obtain a closed overwrapping;
said packet being fed continuously along said wrapping path; and each said projecting lateral portion of the sheet of wrapping material being folded at least partly onto the relative said end surface prior to said second folding step;
the method being characterized by comprising, prior to said pairing step,
a centering step to center the packet with respect to said wrapping path; the centering step being performed by gripping said packet, by means of a first gripper, by two of said lateral surfaces; feeding the packet axially along a respective portion of said wrapping path by means of said first gripper; rotating said first gripper about a turn-around axis crosswise to said wrapping path and to said longitudinal axis so as to position the packet with a first of said two lateral surfaces forward; and transferring said packet to a second gripper, which grips the packet by said two end surfaces.